Automatic telephone system.



1. E. COOLEY.

AUTOMATIC TELEPHONE SYSTEM. Ar'rucmou FILED my 23. 1914.

Patented J an. 16, 1917.

UNITED STATES PATENT OFFICE.

JEROME E. COOLEY, 0F MANHATTAN, KANSAS, ASSIGNOR T0 AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, Av CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Application filed January 28, 1814.

To all whom it may concern:

Be it known that I, Jsnoiun E. Coonur, a citizen of the United States of America, and resident of Manhattan, Riley county, Kansas, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a specification.

My invention relates to improvements in automatic telephone systems, and more particularly to improved means for giving the calling subscriber a busy signal when the called line is busy, and for preventing the apparatus employed in establishing a connection from being unnecessarily tied up when the called line is busy.

' Heretofore, in automatic systems, it has been customary to associate a busy signaling machine with the connector, and when this connector attemptedto establish connection with abusy line, this busy signaling machine was brought into operation to thus inform the callin subscriber that the called line is busy. hen when the calling subscriber hun up his receiver, the connection would be're eased. The trunks'and switches employed. in establishing the connection would thus be inaccessible for further use 4 during the period that the busy signal was being given and until the calling subscriber hung up his receiver. my invention, however, I prevent the switches being tied upl in this manner in that I provide means w ereby all switches employed in establishing a connection will immediately be released when an attempt is made to establish connection with'a busy line, and the busy signaling machine, instead of bein oia-ted with the connector switch, as eretofore, is associated with the individual line switch of the calling line, When this line switch releases for any reason while the callingsubscriber has his receiver oil the hook, the busy si naling machine is connected with the cal mg line to thus give the usual busy signal to the calling subscriber.

These and other features and objects of my. invention will be more readily understood by reference to the accompanying drawing, in which I have illustrated one embodiment of my invention in connection with certain automatic switches of a wellknown type.

Specification of Letters Patent.

Patented Jan. 16, 1917.

Serial No. 813,933.

The drawing shows an. automatic substation and the central oihce apparatus of an automatic telephone system embodying the principles of my invention. The central ollicc equipment shown herein comprises only the so-called line switch and connector switch, but it will be clearly understood by those versed in the art that so called selector switches may be inserted in the system, thereby increasing the capacity ofthe exchange without departing from the principles of my invention. The so-called selector switches may be of a type similar to the selector switch shown in British patent to T. G. Martin No. 1,419 of-1910.

The substation A shown herein may be of any suitable oruapproved type and corn prises the usual receiver 2, transmitter 3, ringer 4 and condenser 5. Being an automatic substation it is also provided with an impulse transmitter or calling device which is represented hereinby a pair of impulse springs 6 and 7 and an impulse wheel 8, which latter is assumed to be controlled through the medium of a finger hole dial (not shown) in such a manner that the impulse springs 6 and 7. may be momentarily separated a number of times corresponding to each digit of the number to be called.

The line switch C'which is associated with the line of the substation A is of the general1 type of line switch shown in British patent to T. G. Martin No. 1419 of 1910, above referred to, the circuits being slightly modified to operate in a system embodying my invention. This line switch comprises, among other details, a plunger (not shown) attached to the nd of a so-called plunger arm 9 which is controlled by the magnet 10.

The magnet 10 comprises two windings, namely, the pull-in winding 11 and the holding or cut-off winding 12, The winding 11 operates both the plunger arm 9'a'nd'thc cutoff armature 15, while the winding 12 is only,

strong enough tooperate the armature 15 I era] type that disseloeezl in ing the springs l6, 17, .15 our]. if] into (in-- gngi-urwmi" with. the springs 20., 21, 22 23 rre iieciiuly: Although on! om.- eel. spy-loge {ill-"15} 1:; ."illuwn, each Mitch is provich-xi with u Humility 1h ems,

each set; fol-min {he lzermml uh line lending: in 2; ruHilQC-iltli. out, lfiinrh trunk lino ml in multi eorres jionuir g up in age in" all the on the group which is conlzmlled hr the switch 1').

The In;

to W. Jam :3 No. 3,501; however, of th the above-.rr.=+.e:nti 1:119 of '5 Switch, plunge tron to anger line,

The '1. general type )1' roomin United jl'tgranted l'l'lareh a and Erick-eon, x modified to adapt the ewmzh system in. 'wl'iirh {he (1 "itrul office uggrparei us is controlled hy impuluwrdelivered over the two sides; of the line in series. The circuits elm otherw"ie slightly modj fierl to operate in a, sytem embodying the prineiples of my invention, The couneccor pro Viclcd with ashefiz (not shown) carrying the wipers 24, and 2%? The shaft is con: trolled. by the -erticel magnet 2? the rotary lnagnei fii u- The umml switch comprising the wiper anal is controlled by the private in 33 in the usual. welhlrnit u n manner The magnet 3% is the isual i'uuggnet The {.vperntions of the iuviteh ere controlled l-l'ui'ough the medium of the ClOlll'lle-(Hlhd line relay 35, through which the calling subscriber re selves talking: current. The calledeuhscriher receives talking eurreufl through the soealled bacil'c-linfidgo relay 36. The ringing relay 37 is the means through which rii'ifging current is applied to the called line.

A general descri wtion. of the apparaius having been given, it will now he explained how a connection is estuhlisluul between e substation A. and a called euhstution (not shown). It will also be explained how, if the called substation is busy.v all of the uppuratus is mitomutioally released and. re turned to normal. posaition, whereby the u periieular by r I trunks are lpt. from being ummlo busy and the calling subscriber is given a lmsy signal through the medium of 1113 u'idiv'irlual line switch C.

,oos

It will he uesuuierl that the number of the rolled substation is 20. Upon the removal of the receiver from. the switch-hook at the substation ."r prermii'atory to mulling; u call, an illfllglZlllfiI ran-cull u: closed tlu'ough the lane reli y 13 of the hue switch C. This cirrui'r extends i l-on; ground (i' through the eprii: s Ij'ci mul 251 (:(H'ldlikih? l il'irough the suns :Ltion A, oondLu-wr ll, :sgzriuge and iii :mil the; llilc relay .23. to leathery B, thence Lhrough iim'l 'r 0 grouiul. The liw; relay lizl, urn-1;) oiiergizing, operates to (hr'e the (ll'ljllll of th. pull-in. winding ll... This circuit extends from ground (,i fihrough the spring-gs: 4' and. Q5, spring" ll) and 4.7, pull-iii wiruiiugg .1]. and the springs 18 imd l? to battery ll. The ull-'12. Wimlii'ig ll. to nous-o the m zri'iure ii) to force 3? and engu lament )riugi-r {Jul 42, roa mutivey, and also opw'oie; lo llungei' on the ulna-5r. our 9 i lo L Z-3.. lnr 'eeivr, epringg ti opens the circuitoi. The line relay 1 helm" f ll iluuurclim; h me u :ui in l i5 3 ,grro mi wim'u; 1.1% fro; 1 The en new of the rit ngs 16 l9 Wit-h the vpriugs. 20 and respectively, extends ihe suhsrril'iers line to 'lz-he line relay of the. connector E. The line role-3* 35-0-1? the ronoector switch ll] is tliereupori energized, cloeing a, oirrnit through the relay 5% This oircuii; extends from grmzml' l through the 00 ml. of lhe springs r m-l 52-3 and the relay to battery B. The relay 50, upon rgizaiug closes the fll'lGYQ-lflflzfitlOnlll hold- 'iii' throu li, the rut-wit? w uiiiig l2. 'ouit exterior; from ground through mui springs 56 and 57, ul l'Tuncl the cu'lw fl' winh lfii The J ling 12.1xpon ,ergisziug, holds; the armature l5 and the who: er 9 in their 'fj'pe'l'lll h'kil pr ions after therii'ruit of the pull '11 winding ishroken by the opening: of the springs -19: and 45. The euergizatiou or the relay 50 also closes 3H1 energizing circuit for the slou acting relay .14 of, the line switch. This-circuit exlends from grouml (31* through the springs and. 55, springs 56 end .57, bank springs; 21 and 17, springs 58 and fiil'ancl the relay 14 lo battery B. The rel-15 14, upon enelw gizirig, (losea circuit. extending from ground, G through the springs 60 and-61 and the rmulurtor (52 to the connector pri Yum hunk 1"(')lll. l1(t'l )3, which guards against the sub-station A being seizbd by a connector switch. The enol'gzizution of the relay 50 also fnj'epnres n cirruii, forthe vertical magnot of" the vounertor by bringing into en-' gagmucnt the springs 6i and (S5 and opens 1,21a,eoav

the circuit of the release ma now operates his calling device for the first I -The vertical magnet 27 ijeceives two im-:

20, ,o posite the second level of bank contacts.

' extends from groundGc t di it 2 of the called number, whereby the su station impulse springs 6 and 7 are operated twice momentarily, each time breaking the circuit of the; connector line relay 35. The relay of the connector being slow acting does not denergize duri the momentary interruptions of its circuit by the line relay 35 and consequently each time the latter deenergizes, an impulse is transmitted through the vertical magnet 27, This circuit extends from ground Gr through the springs 52 and 51, springs 64 and 65, rela 6 vertical magnet 27 and the side switc wiper 29 '(in first position) to battery B.

pulses over thiscircuit andoperates to raise the switch wipers 24, 25 and 26 to a position he relay 67, which was included in series .with the vertical magnet, remains energized during the entire time that impulses are being transmitted through it and operates to c o 33. The circuit forthe private magnet 33 rough the springs 68 and 69 and the private magnet 33 to battery B. After the last impulse is delivcred, the relay 67 opens the circuit of the private magnet 33, which, upon denergizing, permits the side switch to advance from first to second position. The movement of the side switch wiper 29 from first to secand position transfers'the battery connection from the vertical magnet 27 to the rotary magnet 28. The callin subscriber now operates his calling device fir the last digit 0, in response to which the connector line relay operates to transmit ten impulses through the rotary magnet 28 in series with the ii'elay 67, whereby the shaft wipers are vious digit to cause the private magnet 33 rotated onto the contacts of the desired line. This circuit extends from ground GFthrough "the springs 52 and 51, springs 64 and 65, relay 67, springs 70 and 71, 'rotary magnet 28 and the side switch wiper 29 (in second position) to battery B. The relay 67 opcrates in response to the impulses for this digit 1n the same manner as for the pre to advance the side switch one more position, 1'. 6.. from second to third position.

The called substation is equipped with an individual line switch (not'shown) similar in all respects to the line switch 0, so that when the wipers 24, 25 and 26 of the connector E are rotated onto the contacts of the desired line, they are rotated onto conta'cts similar to the contacts 63, 72 and 73 of the line switch C. By the engagement of the side switch wipers 31and 32 with thelr tllllCl-IIJOSllilOl'l contact points the line connection is completed with the" called line.

gnet 34 at the springs 64 and 66. The calling subscriber the circuit of the private magnet si al t Upon the engagement of the wiper 30 with its third-position contact point, acircuit is completed through the cut-oil winding of other connector switch. By the engagement of the side switch wiper 29 with its thirdposition contact point, the circuit. of the ringer relay 37 is closed Thiscircuit-extends from round G 1.11m, h the interrupter 75, re ay 37, springs *and 76 and the side switch wiper 29 to battery "B. p The ringing rela disconnects the callin line from the cal ed line and bridges the ringing current generator R across the called line to e called subscriber. The ringing reay is I energized only through the medium of the interrupter 75. Upon the response of the called so scriber his line is'provide'd with talking current through the windings of the back-bridge relay 36, which relay, upon energizing, closes the circuit through the ringer'cut-ofi relay 7 8. The said circuit extends from ground Gr through the side switch wiper 30 (in third osltion), springs 79 and SOand the relay 8 to battery Hg. The relay 78 upon energizing, interrupts the circuit of the rmging relay 37 at the sprin 77 and 76 and closes-,a locking circuit or itself through the springs 81 and 82 independent of the springs 79 and 80. I

After the conversation is completed, the connection is released by the hanging up of the receiver at the calling substation in the following manner: When the receiver at the substation A is restored to the switch-hook, the separating of the hook-switch springs destroys the energizing circuit of the connector line relay 35. he relay 35 is there'- upon denergized' and opens the circuit of the relay 50. The relay 50, upon ing, completes a circuit extending from ground G through the springs. 52 and springs 6i and 66, offnormal springs 83 and 84: and the release magnet 34 to battery B. The magnet, upon energizing, restores the switch .shaft and side switch wipers to normal position and its own circuit is broken at the oitnormalsprings 83 and 84 when the shaft reaches its lowest position. The relay 50, upon denergizing, also opens the holding circuit for the winding 12 and the-relay 14 of the line switch C at the springs 54 and 55. The line switch C, upon becoming deintermittently energized, allows the plunger arm 9 to return to normal position.

It will now be explained how, when an attempt is made to establish a connection wlth a busyline, the line switch and connector are released and how the release of the line switch connects the busy signaling machine Q with the calling line to thus give the calling subscriber the husv signal.

It the called subscriber is busy, there will be a guarding potential upon the connector private bank contact, just as explained in connection with the line switch C. The connector private wiper 25, upon engaging this guarding contact and before the side switch wipers have passed to third position, completes an energizing circuit through the relay 85. This circuit extends from ground at the private bank contact through the prirate wiper 9,5;side switch wiper 30 (in Sec end position), relay 85, springs 86 and 69 and the private magnet 33 to thebattery B, The relay 85, upon energizing, opens the holding circuit for the winding 12 and the relay Lit of the line switch C. The winding 12, upon deenergizing, allows the armature 1.5 to fallback and the springs 38 and 43 to make contact with the springs 39 and 42, respectively. The plunger arts; 9 is with drawn from the bank of contacts 16 to 23, inclusive, thus opening the circuit of the relay 35 of the connector E at the springs 16, 20 and 19, 23. The deenergization of the line relay 35 allows the connector to release in the manner before mentioned. The springs 38 and 43 making contact with the springs 39 and 42 closes a circuit through the line relay 13 of the line switch C. The relay 14: being slow acting, the relay 13 energizes before the relay 14 has had time to deenergize and. thus completes a holding circuit for the relay 14:. The said circuit extends from ground G through the springs 44 and 45, springs 46 and 87 and the relay 14 to battery B. The relay 14 remains Y energized over the above-traced circuit and retains the circuit of the pull-in winding 11 open at the springs 46 and &7.- The line switch C is thus prevented from tripping and the cut-off armature 15 is-prevented from operating. gizing, closes the contacts 88 and 89 and thus connects the busy signaling machine Q, with the calling line. A busy signal-is thus transmitted to the calling subscriber over the following path: from the busy machine Q through the springs 88 and 89, springs 43 and k2, conductor 41, through the substation A, conductor 40, springs 39 and 38 to ground G and from ground G to the busy machine Q. The subscriber, upon receiving the busy signal, replaces his receiver upon the receiver-hook. ceiver upon the receiverhook allows the switch-hook springs 90 and 91 to separate,-

The relay 13, upon ener-- v The replacing of the re-' thernsea In this manner I prevent the switches and trunks employed in establish 1 ing this connection from being unnecessarily retained in use during the time elapsing between the time when the connector strikes a busy line and the'calling subscriber hangs up his receiver. In this way I am enabled to greatly reduce the number of switches and trunks required in a telephone exchange and thus greatly increase the efiiciency of the systenn It will furthermore be seen that I have devised a very efiicient means for transmitting a busy signal to the calling subscriber by having this signal associated with the individual line switch.

lVhile I have illustrated. my invention in connection with one particular type of auto-- matic system, it will, of course, be understood that it is capable of use with many other forms of systems, and is equally as well adapted for use in connection with semi-automatic systems-that is, systems in two sides of a calling line in series, means for extending a connection from a calling line to said connector switch, and means for automatically releasing said last connection .upon said connector attempting to establish connection with a called line which is busy.

2. In a telephone-system, a plurality of subscribers lines. an automatic connector switch for establishing connection with a called line, said switch provided with op erating magnets for moving the switch first to elect a group of lines and for thereafter moving the switch. to pick out a line in the elected group, means for extending a connectlon from a calling line to said connector switch, said connector switch controlled. over two sides of the calling line in series, means for automatically releasing said last connection upon said connector attempting to establish connection with a called line which s busy, and means controlled by the release of said last connection for releasing said connector; l

3. In a telephone system, a subscribers line, a line switch'individual thereto, means for operating said switch to extend a con nection from said line, a busy signaling machine associated with said switch, and'means controlled by, the released said switch for connecting said busy signaling machlne with the calling line.

4. In a telephone system, a subscribers line, a line switch individual thereto, a busy signaling" machine associated with said switch, means for operating said switch, means for releasing said switch when an at tempt is made to establish connection with a busy line, and means controlled by the release of said switch for connecting said busy signaling machine with the calling line. 5). in a telephone system, a subscriliiers line, a line switch individual thereto, a busy signaling machinev associated with said switch, means for operating said switch, means for releasing said switch. when an attempt is made'to establish connection with a busy line, means controlled by the release a of said switch for connecting said busy sig'- -naling machine with the calling line, and means controlled by the replacing of thereceiver on the hook at the calling siilbstation for disconnecting said busy signaling ma .chine from the calling line.

6. In a telephone system, a calling sub- "scribers; line, a called subscriber-s line, a line switch individual to said calling line, an automatic connector switch adapted to establish connection with' the called line,

means for establishing connection from the line switch to said automatic switch, means I for releasing said line switch when said connectar attempts to make connection with a bus line a bus si alin machine asso- 7 b ciated with said line switch, and means controlled by the release of said line switch for connecting said busy signaling machine with the calling line. i e

7. In telephone system, a calling subscriberfslin'e, a called subscribers line, line switch individual to said calling line, an automatic connector switch adapted to estab lish connection withthe called line, means for establishing connection from the line switcn'to said automatic switch, means for releasing said line switch when said con; nector attempts to make connection with a busy line, a busy signaling machine associated with said line switch, means con trolled by the release of said line switch for connecting said busy signaling machine with the calling line, 'andmieans'controlled by the replacing of the'ieoeiver on the hooln at the calling substation for disconnecting said Inr'a telephone systelma callingiling',

signaling machine ii-om! the calling a line switch therefor for extending a connection from said line, a line relay for said i switch bridged across said line and adapted to'be energized when the subscriber removes his receiver from the-hook, an operating magnet Ior said switch adapted to be energized by the operation of said line relay, and means for preventing the operation of said line relay from closing the circuit of said. operating magnet when said switch is vreleased while the calling subscriber has his receiver off the hook.

9. In atelephone system, a plurality of subscribers lines, an automatic connector switch for establishing connection with a called line, means including an automatic switch for extending connection from a calling line to said connector switch, a holding circuit for said lastancntionedswitch, and

means for opening said holding circuit when said connector attempts to establlsh connec-' tion with a busy line.

10. In a telephone system, aplurality of' subscribers lines, an automatic connector switch for establishing connection with a caller] line, means including an automatic switch for extending connection from a callingline to said connector switch, a holding circuit for said last-mentioned switch, a relay i'nsaid connector, means for energizing said relay when said connector attempts to establish connection with a busy line, and

ing connection with said connector, mean for operating said line switch when the calling subscriber removes his receiver from the hook, a: holding circuit for said line switch, and means for breaking said holding circuit when said connector attempts to establish connection with a busy line to therebyrelease said line switch.

12,111 a telephone system, a plurality of subscribers lines, an automatic connector.

switch for establishing connection with '3, called line, means including a line-switch individual to" the calling line for establishing connection with said'connector, means for operating said line switch when the calling subscriber-removes his receiver from the book, a holding circuit forsaid line switch, means ,for breaking said holding circuit when said connector attempts to establish connection with a busy line to thereby release isaid line switch, and means for preventing said line switch from again operating if the calling subscriber still has his receiver off the hook.

13. In a telephone system, a plurality of subscribers lines, an automaticgconnector onthe hook at the calling substation for from the calling line. I

23. In a telephone system, a plurality of subscribers lines, an automatic connector switch raintrollable over two sides of aline circuit in series for establishing connection with a called line, means including an automatic switch for extending connection from a calling line to said connector switch, a holding circuit for said last-meritioned switch, and means for opening said holding circuit Wl'lOll'SdlL'l connector attempts to es tablish connection with a busy line.

24. In a telephone system, a plurality of :aibscribers lines, an. auttmiatic connector switch controllable over two sides of a line circuit in series for establishing connection with a. called line, means including an automatic switch for extending connection :l'rom a calling line to said connector switch,

a holding circuit for said last-mentioned switch, a relay in said connector, means for energizing said relay when said connector attempts to establish connection with a busy line, and means controlledby the energization of said relay for opening said holding circuit.

25. In atelephone system, a plurality of subscribers lines, an automatic connector switch controllable over two sides of a line circuit in'series for establishing connection with it called line, means including a line switch individual to the calling line for es- \tablishing connection with said connector, means for operating said line switch when the calling subscriber removes-his receiver from the hook, a holding circuit for said line switch, and means for breaking said holding circuit when said connector attei'npts to establish connection with a busy line to thereby release said line switch.

26. In a telephone system, a plurality of subscribers lines, an automatic connector sw-itch'controllable over two sides of a line circuit in series for establishing connection with a called line, means including ahne switch individual to the calling line for establishing connection with said connector, means for operating said line switch when the' calling subscriber removes his receiver from the book, a holding circuit for said line switch, means for breaking said holding circuit when said connector attempts to establish connection with a busy line to there by release said line switch. and means for preventing said line switch from again open ating if the calling subscriber still has his receiver off the hook. v

27. In a telephone system, a plurality of subscribers lines, an automatic connectorswitch controllable over two sides of a line circuit in series for establishing connection with a called line, means including a line switch individual to the callina line for esdisconnecting said busy signaling machine line.

tablishing connection with said connector, means for operating said line switch when the calling subscriber removes his receiver from the hook, a holding circuit for said line switch, means for breaking said holding circuit when said connector attempts to establish connection with a busy line to thereby releasn said line switch,,md means controlled by the release of said line switch for trans mitting a busy signal to the calling subscriber. i

28. In a telephone system, a plurality of subscribers lines, an automatic connector switch controllable over two sides oi? a line circuit in series for establishing connection with 21 called line, means. including, a, line switch individual to' 'thc calling line for establishing connection with. said connector, means for ol'jierating said line switch. when the calling subscriber removes his receiver from the hook, a holding circuit for said line switch, means for breaking said holding circuit when said connector attempts to establish connection with a busy line to thereby release said line switch, means -for preventing said line switch from again opering of said bridge for releasing said c0nnector.

30. In a telephone system, a connector, talking conductorsextending through said connector, said conductors divided into two inductively connected sections, one on the calling subscribers side and one on the called subscribefis side, arelay bridged across the conductors of the calling side for controlling the operation of said connector and means for automatically operating said relay when the connector lands on a busy 31. In a telephone system, a calling line, '31 called line, a pair of progressively movable trunking switches for connecting the two over a talking circuit, means for operating said switches, a release equipment for releasing said switches, a holding circuit separate from the talking conductors for preventing the release of said switches during talking, and means for rendering said holding circuit inoperative wl'ien the called line is busy for releasing said switches.

32. In a telephone system; a calling line, a called line, a pair of progressively mov able trunking switches for connecting the two over a talking circuit, means for operating the said switches over two sides of signaling 'ating magnets switch the calling line in series, a release equipment for releasing said switches, a holding circuit separate from the talking conductors for preventing the release of said switches during talking, and means for rendering said holding circuit inoperative when the called line is busy for releasing said switches.

33. In a telephone system, a plurality of subscribers lines, an automatic connector switch for establishing connection with a called line, said switch provided with operfor -moving the switch first to elect a group of lines and for thereafter moving the switch to pick out a line in the elected group, switch controlled over two sides of a calling line in series, means for extending a connection from. calling line to said connector switch, and a relay for automatically releasing said last connection upon said connector attempting to es tablish connection with it called line which is busy.

34. In a telephone system, a plurality of subscribers lines, an automatic connector "for establishing connection with a called line, said switch provided. with operating magnets for moving the switch first to elect a group of lines and for thereafter moving the switch to pick outa line in the elected group, means for extending connection from a calling line to said connector switch, said connector switch over two sides or the calling line in series, means for automatically releasing last connection upon said connector attempting to establish connection with a called line which busy, and a relay controlled by the release of said last connection for releasing said connector,

35. In a telephone system, a subscribers line, a line switch individual thereto, means for operating said switch to extend a corn nection from said line, a busy signaling machine associated with said switch, and a line relay controlled by the release of said switch for connecting said busy signaling machine with the calling line.

36. In a telephone system, a subscribers line, a line switch individual thereto, a busy machine associated with ,said switch, means for operating said switch, a circuit "for releasing said switch when an attempt is made to establish connection with a busy line, and electromagnetic means controlled jointly over said circuit and the said subscribefs line for connecting said busy signaling machine with the calling line.

37. ln'a telephone system, a calling line, a line switch therefor for extending a connection from said line, a line relay for said switch bridged across said line and adapted to be energized when the subscriber removes his receiver from the hook,-an operating magnet for said switch adapted to be enercontrolled gized by the operation oi: said line relay, a second relay forpreventing the operation of said line relay from closing the circuit of said operating magnet when said switch is released 'while the calling subscriber has his receiver oil the hook, and a busy signaling circuit closed by the encrgization of said line relay'while the said operating magnet remains inoperative. I

38. Ina telephone system, a plurality of subscribers lines, an automatic connector switch for establishing connection with a called line, means including a line switch individual to the calling line for establishing connection with said connector, means for operating said line switch when the calling subscriber removes his receiver from the book, a holding circuit for said line switch, means for breaking said holding circuit when said connector attempts to establish connection with a busy line to thereby release said line switch, and a circuit controlled by the re lease of said line switch for transmitting a busy signal to the calling subscriber.

39. In a telephone system, a plurality of subscribers lines, an automatic connector switch for establishing connection with a called line, means including a line switclrelf the hook, and a circuit controlled by the release of said line switch for transmitting a busy signal to the calling subscriber. I

10. In a telephone system, a plurality of subscribers lines, means including a plurality of automatic switches controllable over two sides of a line circuit in series fdr extending a connection from a calling line to a called line and a relay for automatically-z'releasing all of the switches in said connuition when one of said switches attempt; to make connection with a called line which is busy.

41. In a telephone system, a plurality of subscribers lines, an automatic connector switch controllable over two sides of a line circuil iii series for establishing connection with a. called line, means for extending a connection from a calling line. to said connector switch, and a busy test relay for automatically releasing said last connection upon said connector attempting to establish connection with a called line which is busy.

I 42. In a telephone system, a subscribers line, a line switch individual thereto, a busy signaling machine associated with said switch, means controllable over two sides of a line circuit in series for operating said switch, means for releasing said switch when an attempt is made to establish connection with a, busy 1111c, and a. relay controlled thereafter over the said subscribers line for connecting said busy signaling machine thereto.

In.a telephone system, a connector, 1 front bridge in said connector for. controlling the operation thereof, a test relay for opening said bridge when said connector lands on a busy line, 'and a. circuit controlled by the opening of said bridge forrelessing said connector.

Signed by me at Chica 0, Cook county" 

